v0.0.8c

Fixes memory-safety and correctness bugs in gmscuopt.c:
- Reject models with SOS1/SOS2/semi-integer variables instead of
  leaving variable_types[] uninitialized.
- Fix broken #ifdef/#if defined(CUOPT_INSTANTIATE_DOUBLE) checks that
  permanently dead-coded the float-precision fallback path.
- Disable mipstart/LP warm-start when prob_read is set to avoid a
  buffer size mismatch.
- Use CUOPT_METHOD/CUOPT_PRESOLVE/CUOPT_DUAL_POSTSOLVE constants
  instead of hardcoded option strings.
- Check status of previously-unchecked gmoGetRowSparse/gmoGetRowQ
  calls and presolve/dual_postsolve parameter queries.

Also makes build-link.sh robust to both venv/ and .venv/ layouts, and
adds capability_tests/*.gms models exercising the SOS/semi-integer
rejection.